Image display apparatus, image processing apparatus and method to output an image with high perceived resolution

Abstract

An intermediate image generating means ( 1 ) generates a horizontal intermediate image (D 1 h ) and a vertical intermediate image (D 1 v ) by extracting components of an input image (DIN) in a particular frequency band; an intermediate image processing means ( 2 ) generates a horizontal image (D 2 Bh) and a vertical image (D 2 Bv) by performing non-linear processing ( 2 A) and high-frequency component generation ( 2 B); an intermediate image (D 2 ) is obtained by combining these horizontal and vertical images by performing weighted addition for each pixel and is added ( 3 ) to the input image (DIN) to obtain an enhanced output image (DOUT). Even if the input image includes a fold-over component on the high-frequency side or does not include an adequate high-frequency component, adequate image enhancement processing can be carried out.

What is claimed is: 
     
       1. An image processing apparatus including an image processing circuit, said image processing circuit comprising:
 an intermediate image generating unit configured to generate a first horizontal intermediate image by extracting a horizontal component in a particular frequency band in an input image and a first vertical intermediate image by extracting a vertical component in a particular frequency band in the input image; 
 an intermediate image processing unit configured to generate a second intermediate image from the first horizontal intermediate image and the first vertical intermediate image; and 
 a first adding unit configured to add the input image and the second intermediate image; wherein 
 the intermediate image processing unit comprises: 
 a horizontal zero-crossing point decision unit configured to identify a point where the pixel value in the first horizontal intermediate image changes from positive to negative or from negative to positive as a zero-crossing point; and 
 a horizontal signal amplifying unit that generates a horizontal non-linearly processed image by amplifying the pixel value of each pixel in the vicinity of the zero-crossing point, among the pixels forming the first horizontal intermediate image, by an amplification factor greater than 1; 
 a horizontal high-frequency component image generating unit configured to generate a second horizontal intermediate image by extracting only a high-frequency component in the horizontal non-linearly processed image; 
 a vertical zero-crossing point decision unit configured to identify a point where the pixel value in the first vertical intermediate image changes from positive to negative or from negative to positive as a zero-crossing point; 
 a vertical signal amplifying unit that generates a vertical non-linearly processed image by amplifying the pixel value of each pixel in the vicinity of the zero-crossing point, among the pixels forming the first vertical intermediate image, by an amplification factor greater than 1; 
 a vertical high-frequency component image generating unit configured to generate a second vertical intermediate image by extracting only a high-frequency component in the vertical non-linearly processed image; and 
 a second adding unit configured 
 to add the first horizontal intermediate image, the first vertical intermediate image, the second horizontal intermediate image, and the second vertical intermediate image, and 
 to output a resulting sum as the second intermediate image; and wherein 
 the second adding unit comprises at least one of 
 a first horizontal-vertical combining unit configured to take a weighted sum of the first horizontal intermediate image and the first vertical intermediate image, and 
 a second horizontal-vertical combining unit configured to take a weighted sum of the second horizontal intermediate image and the second vertical intermediate image. 
 
     
     
       2. The image processing apparatus of  claim 1 , wherein
 the second adding unit further comprises a first weighting coefficient generating unit configured to determine a first weighting coefficient from the first horizontal intermediate image and the first vertical intermediate image, and 
 at least one of the first horizontal-vertical combining unit and the second horizontal-vertical combining unit 
 uses the first weighting coefficient in taking the weighted sum. 
 
     
     
       3. The image processing apparatus of  claim 2 , wherein the first weighting coefficient generating unit comprises:
 a first edge direction estimating unit configured to determine an edge direction estimation quantity corresponding to an edge direction in the input image from the first horizontal intermediate image and the first vertical intermediate image; and 
 a first weighting coefficient determining unit configured to determine the first weighting coefficient from the first edge direction estimation quantity. 
 
     
     
       4. The image processing apparatus of  claim 3 , wherein the first edge direction estimating unit outputs a difference between absolute values of pixels in the first horizontal intermediate image and the first vertical intermediate image as the first edge direction estimation quantity. 
     
     
       5. The image processing apparatus of  claim 4 , wherein the first weighting coefficient determining unit:
 determines a weighting coefficient for the first horizontal intermediate image from a characteristic that increases monotonically with respect to the first edge direction estimation quantity; and 
 determines a weighting coefficient for the first vertical intermediate image from a characteristic that decreases monotonically with respect to the first edge direction estimation quantity; and wherein 
 the sum of the weighting coefficient for the first horizontal intermediate image and the weighting coefficient for the first vertical intermediate image satisfies a relationship of always remaining constant. 
 
     
     
       6. The image processing apparatus of  claim 2 , wherein the second adding unit further comprises:
 a second weighting coefficient generating unit configured to determine a second weighting coefficient based on the second horizontal intermediate image and the second vertical intermediate image; and wherein 
 the first horizontal-vertical combining unit uses the first weighting coefficient in taking the weighted sum, and 
 the second horizontal-vertical combining unit uses the second weighting coefficient in taking the weighted sum. 
 
     
     
       7. The image processing apparatus of  claim 6 , wherein the second weighting coefficient generating unit comprises:
 a second edge direction estimating unit configured to determine an edge direction estimation quantity corresponding to an edge direction in the input image, based on the second horizontal intermediate image and the second vertical intermediate image; and 
 a second weighting coefficient determining unit configured to determine the second weighting coefficient from the second edge direction estimation quantity. 
 
     
     
       8. The image processing apparatus of  claim 7 , wherein the second edge direction estimating unit outputs a difference between absolute values of pixels in the second horizontal intermediate image and the second vertical intermediate image. 
     
     
       9. The image processing apparatus of  claim 8 , wherein the second weighting coefficient determining unit:
 determines a weighting coefficient for the second horizontal intermediate image from a characteristic that increases monotonically with respect to the second edge direction estimation quantity; and 
 determines a weighting coefficient for the second vertical intermediate image from a characteristic that decreases monotonically with respect to the second edge direction estimation quantity; and wherein 
 the sum of the weighting coefficient for the second horizontal intermediate image and the weighting coefficient for the second vertical intermediate image satisfies a relationship of always remaining constant. 
 
     
     
       10. The image processing apparatus of  claim 1 , wherein the intermediate image generating unit comprises:
 a first horizontal high-frequency component image generating unit configured to generate a first horizontal high-frequency component image by extracting a high-frequency component equal to or greater than a first prescribed horizontal frequency by using pixels in a horizontal vicinity of each pixel in the input image; 
 a first vertical high-frequency component image generating unit configured to generate a first vertical high-frequency component image by extracting a high-frequency component equal to or greater than a first prescribed vertical frequency by using pixels in a vertical vicinity of each pixel in the input image; 
 a first horizontal low-frequency component image generating unit configured to generate the first horizontal intermediate image by extracting only a low-frequency component equal to or less than a second prescribed horizontal frequency in the first horizontal high-frequency component image; and 
 a first vertical low-frequency component image generating unit configured to generate the first vertical intermediate image by extracting only a low-frequency component equal to or less than a second prescribed vertical frequency in the first vertical high-frequency component image. 
 
     
     
       11. The image processing apparatus of  claim 10 , wherein:
 the second horizontal high-frequency component image generating unit generates the second intermediate image by extracting only the high-frequency component equal to or greater than a third prescribed horizontal frequency by using pixels in the horizontal vicinity of each pixel in the horizontal non-linearly processed image, and 
 the second vertical high-frequency component image generating unit generates the second vertical intermediate image by extracting only the high-frequency component equal to or higher than a third prescribed vertical frequency by using pixels in the vertical vicinity of each pixel in the vertical non-linearly processed image. 
 
     
     
       12. An image display apparatus comprising the image processing apparatus of  claim 1 . 
     
     
       13. A method for processing an image by utilizing an image processing circuit, the method comprising:
 an intermediate image generating step of generating, by utilizing an intermediate image generating unit included in said image processing circuit, a first horizontal intermediate image by extracting a horizontal component in a particular frequency band in an input image and a first vertical intermediate image by extracting a vertical component in a particular frequency band in the input image; 
 an intermediate image processing step of generating, by utilizing an intermediate image processing unit included in said image processing circuit, a second intermediate image from the first horizontal intermediate image and the first vertical intermediate image; and 
 a first adding step of adding the input image and the second intermediate image; wherein 
 the intermediate image processing step comprises: 
 horizontal zero-crossing point decision step configured to identify a point where the pixel value in the first horizontal intermediate image changes from positive to negative or from negative to positive as a zero-crossing point; and 
 a horizontal signal amplifying step that generates a horizontal non-linearly processed image by amplifying the pixel value of each pixel in the vicinity of the zero-crossing point, among the pixels forming the first horizontal intermediate image, by an amplification factor greater than 1; 
 a horizontal high-frequency component image generating step configured to generate a second horizontal intermediate image by extracting only a high-frequency component in the horizontal non-linearly processed image; 
 a vertical zero-crossing point decision step configured to identify a point where the pixel value in the first vertical intermediate image changes from positive to negative or from negative to positive as a zero-crossing point; 
 a vertical signal amplifying step that generates a vertical non-linearly processed image by amplifying the pixel value of each pixel in the vicinity of the zero-crossing point, among the pixels forming the first vertical intermediate image, by an amplification factor greater than 1; 
 a vertical high-frequency component image generating step configured to generate a second vertical intermediate image by extracting only a high-frequency component in the vertical non-linearly processed image; and 
 a second adding step of adding the first horizontal intermediate image, the first vertical intermediate image, the second horizontal intermediate image, and the second vertical intermediate image, and outputting a resulting sum as the second intermediate image; and wherein 
 the second adding step includes at least one of 
 a first horizontal-vertical combining step of taking a weighted sum of the first horizontal intermediate image and the first vertical intermediate image, and 
 a second horizontal-vertical combining step of taking a weighted sum of the second horizontal intermediate image and the second vertical intermediate image.